2. Stationary: sources of
air pollution other than transportation (e.g., power plants)
Mobile: air pollution from transportation

3. Primary pollutants enter
the air directly as the pollutant
Secondary pollutants are formed in the air through chemical reactions between
primary pollutant(s) and one or more air components, often in sunlight (photochemical
smog).

4. Acute effects are caused
by short duration exposure and/or have immediate effects
Chronic effects are caused by long duration exposure and/or have long term effects.

5. Chemical nature: how
active and harmful the pollutant is.
Concentration: amount of pollutant per volume.
Persistence: how long the pollutant stays around before breaking down.

8. Criteria air pollutants
have maximum national ambient air quality standards (NAAQS) -- maximum concentration
in air.
Noncriteria air pollutants have emission standards -- maximum that can come
out of a smokestack.

9. When the temperature
of the air at ground level is cooler than the air just above it, then a temperature
inversion occurs.

10. Temperature inversions
occur when cool air is created under or slips under relatively warmer air at
ground level.

11. Because the cool air
just sits on the ground and does not mix, air pollutants become more concentrated
in this cooler layer at the ground level where we breathe.